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Author Topic: Fuji X T-2 lossless compressed & dng conversion  (Read 4206 times)

Eric Brody

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Fuji X T-2 lossless compressed & dng conversion
« on: September 27, 2016, 01:41:05 pm »

Now that I am using lossless compressed files on my Fuji X T-2, I wondered about these files and dng conversion. I have converted proprietary files, NEF, RAF, to dng for some time now. However, last night, after a lovely walk at the Steigerwald National Wildlife Refuge in nearby Washougal, Washington, I had another revelation. I did what I always do now, connected the camera to the computer with the USB3 cord (so I don't have to fiddle with easy to lose and misplace SD cards), downloaded my images and automatically converted them to dng. To my surprise, the RAF compressed files, which are in the 23MB range, doubled in size upon dng conversion in LR6.7! Initially I was not paying attention to file size, assuming that the dng conversion would save space as it does with uncompressed files. Uncompressed files, in the 48MB range shrink to <40MB files with dog conversion.

To conclude, if you use lossless compression on Fuji X T-2 files, leave them as RAF files, do not convert to dng, at least to save space, because you do not. If you use uncompressed, and I cannot see why, based on my previous question, dng conversion does save some space on the card and the computer as well.

Interesting.

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john beardsworth

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Re: Fuji X T-2 lossless compressed & dng conversion
« Reply #1 on: September 27, 2016, 02:01:36 pm »

It is quite possible that a DNG would be bigger than the original raw file, Eric, though usually they are smaller. The extent to which they are smaller - well, that varies. So bigger is possible.

The reason may be better algorithms by Fuji, or suboptimal algorithms by Adobe when handling XTrans files. But you might want to review your options when converting to DNG. For instance, does the DNG contain a full size JPEG preview - that would increase the DNG size as the RAF only contains a 1980x1280 image. Have you embedded the raw file, which would certainly increase the DNG's size, or is there fast load data? Changing any of these options would have a noticeable effect.

That said, reduced file size is usually a happy by-product of DNG conversion, not the reason to do it in the first place.
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sandymc

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Re: Fuji X T-2 lossless compressed & dng conversion
« Reply #2 on: September 27, 2016, 03:11:57 pm »

The compression algorithm that Fuji are using is considerably more advanced than the lossless JPEG algorithm that is used for DNG compression. The choice of the lossless JPEG algorithm for DNG was probably driven more by a desire to maximize compatibility than a desire for the smallest possible file sizes. So yes, converting compressed RAFs to losslessly compressed DNGs will pretty much always result in larger file size. The price you pay for a documented file format vs an undocumented one.
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E.J. Peiker

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Re: Fuji X T-2 lossless compressed & dng conversion
« Reply #3 on: September 28, 2016, 02:16:25 am »

Check your DNG conversion settings.  The doubling in size is likely due to your choosing to embed the original RAW format in addition to the DNG format into the DNG file.  Take a look at this and in the section marked #4, my guess is that you have the preferences set to embed the original rather than don't embed the original:
https://helpx.adobe.com/photoshop/using/adobe-dng-converter.html

Also see here for specifics on DNG conversion in LR:
https://helpx.adobe.com/lightroom/help/photos.html#convert_photos_to_dng
« Last Edit: September 28, 2016, 02:20:42 am by E.J. Peiker »
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john beardsworth

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Re: Fuji X T-2 lossless compressed & dng conversion
« Reply #4 on: September 28, 2016, 02:36:11 am »

Check your DNG conversion settings.  The doubling in size is likely due to your choosing to embed the original RAW format in addition to the DNG format into the DNG file.

Yes, I also suspected this - compressed raf's seem to grow from 25mb to 35mb on average.
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Eric Brody

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Re: Fuji X T-2 lossless compressed & dng conversion
« Reply #5 on: September 28, 2016, 07:26:54 pm »

Thanks EJ, sandymc, and John for your insights. I just looked at my LR import dng settings (this darn computer keeps changing "dng" to "dog" grrrr, pun intended).

It goes as follows: File extension dng
                           Compatibility: Camera Raw 7.1 and later
                           JPEG Preview: Full Size
                                   Embed Fast Load Data: √
                                   Embed Original Raw File: NOT CHECKED

I don't know if that will change any of your thoughts. Regardless, this is interesting and I appreciate the help.
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sandymc

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Re: Fuji X T-2 lossless compressed & dng conversion
« Reply #6 on: September 30, 2016, 06:34:44 am »

I did quick experiment on some Fuji RAFs I had around (a mix of X-T2 and X-Pro2, both of which have +-50 Mb uncompressed file size):

FileOriginal Size (MB)             DNG Compressed Size (MB)
Compressed RAF 122.332.2
Compressed RAF 228.134.5
Uncompressed RAF 1     50.429.7
Uncompressed RAF 2     50.525.6

So (a) compression ratio varies, as you'd expect, but (b) typically the Fuji compression is more efficient that the DNG compression, also as you'd expect. IMHO, no mystery here.
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john beardsworth

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Re: Fuji X T-2 lossless compressed & dng conversion
« Reply #7 on: September 30, 2016, 07:32:27 am »

With compressed, I get an average of 25mb for 100 RAF files,  35Mb for the DNGs. It's not just more efficient compression though - it's also the greater size of the DNGs' embedded JPEG previews, plus other stuff like the fast load data cache.

In any case, it's not a reason for converting, or for not converting.
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